In the field of semi-conductive crystal, powders of metal compound containing oxygen such as lithium niobate, niobic acid tantalum or barium titanate is employed as material of optical crystal; powders of metal compound containing oxygen such as bismuthic acid barium, bismuthic acid silicon or bismuthic acid germanium is employed as material of nonlinear crystal; and powders of metal compound containing oxygen such as lithium niobate or lithium tantalate is employed as material of magneto-optical crystal. For example, lithium niobate is known as a transparent crystal without rendering color or tinted with pale yellow, and as revealing ferroelectricity. Also, surface acoustic wave devices, Q-switches, optical modulators, optical switches and so on that took advantages of electro-optic effect, nonlinear optical effect, ultrasonic propagation, piezoelectric effect, etc. as the characteristics of lithium niobates are put into practical use.
Conventionally, the powders of metal compound containing oxygen are produced in general by sol gel method, sintering method or sputtering method. Japanese Unexamined Patent Application Laid-Open Nos. Hei 5-9023, Hei 7-21831, Hei 9-208227, 2000-113898 and 2002-356326 disclose the sol-gel method, in which, for example, the powders of metal compound containing oxygen are obtained by dissolving several kinds of metal alkoxide in amine, hydrolyzing and adding a precipitant, thereafter drying precipitation. Japanese Unexamined Patent Application Laid-Open No. Hei 10-338524, for example, discloses the sintering method, in which the powders of metal compound containing oxygen are obtained by mixing several kinds of metal oxide and sintering the resultant mixture. Further, Japanese Unexamined Patent Application Laid-Open No. Hei 8-277467 discloses the sputtering method, in which the powders of metal compound containing oxygen are obtained after repeating the sintering and crushing the sintered objects several times, hot pressing and sputtering the sintered objects with aiming them as a target.